The present invention relates to a structure for mounting a fuel pump to an engine. More particularly, this invention relates to the structure for mounting the pump to an engine of an outboard motor having a vertically extending crankshaft.
Structures for mounting fuel pumps on engines are known from, for example, Japanese Utility Model Post-Exam Publication No. SHO 52-24672 and Japanese Patent Laid-Open Publication No. HEI 10-9078.
A fuel pump disclosed in the publication No. SH 052-24672 is attached directly to a metal cylinder head cover disposed on a cylinder head of an engine. The fuel pump includes a plunger disposed in abutment on a valve rocker arm of the engine. The valve rocker arm is arranged to pivot to thereby drive the plunger. Driving the plunger actuates the fuel pump.
The publication No HEI 10-9078 discloses fuel pumps mounted on an engine of an outboard motor including a vertically extending crankshaft and plural cylinders.
More specifically, the fuel pumps are positioned outside a vertically elongated cylinder head cover of the engine and have horizontally oriented plungers. The plungers are mounted directly to a cylinder head of the engine. The cylinder head cover is made from metal.
The fuel pumps as disclosed in the above publications are attached to the cylinder head covers through bolts or the like. The cylinder head covers are made from metal such as aluminum alloy.
An outboard motor including a large-sized, high-power engine such as a V-6 engine is preferably lightweight for ease attachment to or detachment from a hull of a boat. In other words, the engine which is the heaviest among components of the outboard motor needs to be reduced in weight. A cylinder head cover which covers rocker arms and the like disposed outside the cylinder head of the engine is preferably made from synthetic resin so as to render the engine lightweight.
The cylinder head cover made from synthetic resin is smaller in strength or rigidity than that made from metal. It is thus difficult to mount the fuel pumps, as disclosed in the above publications, to the cylinder head cover of synthetic resin.
One may propose to mount the fuel pumps to any members other than cylinder head cover. For such an application, however, the outboard motor should be provided with additional members for driving the fuel pumps. This leads to the increased number of components provided around the engine. The members for driving the fuel pumps would be complicated in construction.
An object of the present invention is to provide a structure for advantageously mounting a fuel pump to an engine including a cylinder head cover made from synthetic resin, such that the engine is made lightweight.
Another object of the present invention is to provide an outboard motor including the lightweight engine.
According to one aspect of the present invention, there is provided a structure for mounting a fuel pump to an engine, comprising: a cylinder head of the engine; a valve drive mechanism for driving the fuel pump, the valve drive mechanism being mounted to the cylinder head; a cylinder head cover covering the cylinder head and the valve drive mechanism; and the fuel pump being mounted to the cylinder head with the cylinder head cover held therebetween.
The fuel pump is mounted to the cylinder head of increased rigidity, and hence the cylinder head cover which covers the cylinder head can be made from material smaller in rigidity than the cylinder head cover.
The fuel pump is disposed outside the cylinder head cover. More specifically, the fuel pump is mounted to the cylinder head with the cylinder head cover held therebetween. This allows the cylinder head cover to be held to the cylinder head.
The cylinder head cover can be fastened to the cylinder head without excessive load being applied to the cylinder head cover.
The fuel pump is driven by the valve drive mechanism provided at the cylinder head.
There is no need to mount the fuel pump to any member other than the cylinder head. In other words, driving the fuel pump can be achieved without requiring additional, particular members for driving the fuel pump.
In a preferred form of the present invention, the cylinder head is made of synthetic resin.
In a further preferred form of the present invention, the structure further comprises a support base member attached to the cylinder head, the support base member, the cylinder head cover, and a base sheet of the fuel pump being coupled together by plural bolts, the base sheet being positioned in parallel to the support base member.
With this arrangement, the fuel pump is securely mounted to the cylinder head cover and the support base member.
The fuel pump has the base sheet separable from a body thereof. This arrangement is useful for maintenance of the fuel pump.
In a further preferred form of the present invention, the fuel pump includes a diaphragm to be driven by the valve drive mechanism through a plunger.
The fuel pump thus arranged can efficiently supply fuel towards the engine. The supply of fuel can be effected using the valve drive mechanism.
In a still further preferred form of the present invention, the engine includes vertically extending crankshaft, the cylinder head and the cylinder head cover being vertically oriented, the fuel pump being horizontally oriented, the engine being used in an outboard motor.
Since the cylinder head cover is made of synthetic resin, the engine can be reduced in weight to thereby render the outboard motor lightweight. Such a light weight out board motor is readily attached to or detached from a stern of a boat. Further, the outboard motor of reduced weight is easy to handle. The fuel pump can be disposed outside the cylinder head cover of synthetic resin in the same way the former is disposed outside a metal cylinder head cover. The fuel pump is to be driven by the valve drive mechanism. The outboard motor may include a large-sized engine of large engine capacity to provide an increased output.
In a still further preferred form of the present invention, the cylinder head and the cylinder head cover are disposed at a rear part of the outboard motor, the outboard motor including an intake manifold disposed behind the fuel pump, the intake manifold having a recessed portion formed therein, the recessed portion receiving part of the fuel pump.
Because the recessed portion of the intake manifold receives part of the fuel pump, the outboard motor extends a reduced distance along a front-and-rear direction. In other words, the outboard motor can be made compact.